1. Field of the Invention
The present invention relates to an ink jet printing method and an ink jet printing apparatus printing apparatus which print an image on a print medium by using an ink jet print head having a nozzle array in which nozzles for ejecting ink are arranged with a high density.
2. Description of the Related Art
With the diffusion of information processing devices and communication devices (e.g., computer, word processor), output devices for outputting digital image according to digital image information processed by the information processing devices have been increasingly required. One of these output devices is an ink jet printing apparatus printing apparatus that ejects ink droplets to form dots on a print medium to form an image. This ink jet printing apparatus printing apparatus has been widely used. This ink jet printing apparatus printing apparatus uses a print head that is designed, in order to improve the printing speed and the resolution of a printed image, to include a great number of integrated and arranged ejecting sections (hereinafter also referred as nozzles). The ejecting section consists of an ink ejecting port for ejecting ink droplets, a fluid path, and a printing element or the like.
Furthermore, there has been recently another demand for the output of a color printed image. Thus, an ink jet printing apparatus printing apparatus for printing a color image performs a printing operation using not only a print head for ejecting black ink but also print heads for ejecting a plurality of color inks. In the printing operation, the print heads have no contact with a print medium, thus providing a printing operation with low noise. The ink jet printing apparatus printing apparatus also can print an image having a high resolution with a high speed by arranging the nozzles with a higher density. Furthermore, this type of ink jet printing apparatus printing apparatus does not require a special processing (e.g., development, fixing) to a to-be-printed material (e.g., plain paper). Thus, this type of ink jet printing apparatus printing apparatus has various advantages such as the one providing a high quality image with a low cost. An on-demand-type ink jet printing apparatus printing apparatus in particular can provide a color image easily and can be downsized and simplified and thus is expected to create a growing demand in the future. With the increasing demand for a color-printed image, ink jet printing apparatus printing apparatuses are required to provide an image having a higher quality with a higher speed.
On the other hand, with the background of the recent technical progress for the integrated arrangement of nozzles, a print head having a further higher density and a longer length is becoming possible. Generally, a print head having a high density and a long length is called a long print head. This long print head can increase the width of a region that can be printed on a print medium by one printing scan to the print medium when compared to a case where a conventional short print head is used. Thus, this technique has been further developed as a useful technique for realizing a high-speed printing that has been conventionally impossible while maintaining a high image quality equal to that of a conventional design.
However, in the case of the ink jet printing apparatus printing apparatus as described above that uses a long print head having a high density, a problem as described below may be caused.
Specifically, when a long print head in which nozzles are arranged with a high density simultaneously ejects a great number of ink droplets while performing a printing scan by the print head or a scan of a print medium with a high speed, the print head and the print medium have therebetween irregular air current (eddy flow). This causes a problem that positions to which ink droplets land on the print medium are fluctuated. Furthermore, it has been known that the eddy flow between the print head and the print medium has a significant influence on how the ink droplets are ejected, which is also one of the causes of the deterioration of an ink landing accuracy. Another problem is that the fluctuation of the ink landing positions as described above causes the image to have a stripe-like or spiral-like uneven density, remarkably deteriorating the image quality. This has been hindrance to the realization of the printing of a high-quality image with a high speed.
As a technique for solving the stripe-like uneven density as described above, techniques disclosed in Japanese Patent Laid-Open No. 2001-18376 or Japanese Patent Laid-Open No. 2002-96455 are known.
Japanese Patent Laid-Open No. 2001-18376 discloses a technique in which nozzle arrays provided in a print head are divided to the printing ones and no-printing ones with a fixed pitch and the fixed pitch is further minutely divided. This technique can cause the stripe uneven density (stripe-uneven printing) to be the one that is difficult to be visually recognized.
Japanese Patent Laid-Open No. 2002-96455 also discloses a mask pattern for allocating, when a printing method is used by which a plurality of main scans complete an image within the same printing region, the operation for providing the image within the same printing region to a plurality of main scans. This mask pattern is set so that the end part side of the nozzle arrays have a higher thinning-out ratio than that of the center side. The use of this mask pattern can reduce the frequency at which the end part nozzle is used, thereby eliminating the uneven density caused by twisted eject from the end part nozzle.
However, the techniques according to the above Patent References still have room for improvement in that deterioration of an image due to eddy flow caused between a print head and a print medium is not sufficiently avoided. Specifically, the eddy flow caused between a print head and a print medium may be caused not only at the end part of the nozzle array but also at the entire region of the nozzle array. Influence by eddy flow between nozzle arrays also cannot be ignored. Thus, it is difficult for only the conventional techniques to avoid the deterioration of an image due to the generation of the eddy flow.
What is required for ink jet printing apparatus printing apparatuses in the future is to realize a printing of an image with both of a further higher speed and a further high quality. To do so, the deterioration of the quality of an image due to the eddy flow as described above needs to be improved.